Business Insider UK was allowed inside a traditional olive mill in Italy, to see the process behind one of the world’s most-used cooking ingredients.
Olive oil comes in many varieties and flavours that change depending on soil, climate, age, and production.
The most refined olive oil is called ‘extra virgin.’ To be called so, the olives need to be crushed within 24 hours. They also need to be ‘cold pressed,’ meaning the oil is extracted mechanically at room temperature without the use of heat or chemicals.
While modern mills use steel drums to cold-press their olives, some smaller, often family-run mills are still making it the old-fashioned way with giant granite wheels.
The mill we visited in Monopoli, south Italy, produces around 800 litres per day of extra virgin olive oil, crushing about 5,000 kg of olives.
Harvested olives enter the mill on a conveyor belt, losing around 90% of the leaves. The last 10% is ground into a paste with olives and pits.
The paste then moves into a kneading machine, which helps break the paste down into water and oil. It’s then spread over large fibre discs that are piled up and pressed for around 2.5 hours.
Finally, the oil is separated from water and ready to be sold, or it can be filtered to give it a clearer appearance. Filtering is done through a funnel and cotton wool. While filtered oil has a longer shelf life, it has less flavour than the unfiltered product.
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